The parks dept. puts such a tremendous value on trees of this size that they may have inspected it and felt they could leave it. It happens all the time, they may be the most pompous and ignorant people that the city employs. When these trees show any sign of decay they should be removed and replaced with a proper curb tree. That's what I would want in front of my home. I would not want to deal with the property damage a falling tree could cause or something worse such as the injury or even the death of an innocent person.